The kidney has three major physiological functions: excretory, endocrine, and metabolic. However, regulation and excretion of water, minerals, and other nutrients is the most important function of the kidneys. Metabolic waste products eliminated by the kidneys include urea, creatinine, uric acid, hemoglobin degradation products, and hormone metabolites. The kidneys also play a role in arterial pressure regulation by secreting vasoactive substances such as renin. In addition, the kidneys secrete erythropoietin, which stimulates red blood cell production, and produce 1,25-dihydroxy vitamin D3, the active form of vitamin D. Any of these functions may be impaired in renal disease leading to disruptions in the nutritional status of the patient. TEXTBOOK OF MEDICAL PHYSIOLOGY 315 (Guyton & Hall, 9th ed. 1996).
Renal disease is one of the leading causes of morbidity, with millions of individuals affected annually. Generally, renal disease may be classified into two categories: 1) acute renal failure and 2) chronic renal failure. Acute renal failure is characterized by a sudden reduction or cessation of renal function. In contrast, chronic renal failure refers to a progressive loss of renal function, usually a result of an underlying pathological condition. For example, immunological disorders such as lupus erythematosus, metabolic disorders such as diabetes mellitus and hypertension, and infectious diseases such as tuberculosis can lead to chronic renal failure. As renal function continues to deteriorate, patients develop end-stage renal failure (ESRD) that eventually requires dialysis treatment or transplantation. Id. at 413.
Patients with chronic renal failure typically develop generalized edema, acidosis, and uremia, an accumulation of nitrogenous metabolites in the blood. To alleviate these symptoms, patients are placed on dietary therapy or dialysis. The protein-restricted diet prescribed for renal patients is generally deficient in vitamins such as folate, the B vitamins, and vitamin C. HANDBOOK OF NUTRITION AND THE KIDNEY 42 (Mitch & Klahr, eds., 3rd ed. 1998) (hereinafter “HANDBOOK”). In addition, the dialysis procedure itself may remove vitamins and nutrient compounds. Gastrointestinal absorption of vitamins may be also altered in patients suffering from chronic renal failure. Makoff, 25 MINER. ELECTROLYTEMETABOL. 349-351 (1999).
Compliance with the restrictive renal diet may also result in deficiencies in trace minerals such as zinc and selenium. Highly protein-bound minerals may be lost in excessive amounts in patients with proteinuria. Zima et al., 17 BLOOD PURIF. 182-186 (1999). Furthermore, it has been shown that plasma levels of selenium are decreased in dialysis patients. HANDBOOK, at 43. Poor nutritional status and insufficient levels of vitamins and minerals may place renal patients at higher risk for diseases such as anemia, infections, and cardiovascular disease, or aggravate pre-existing conditions such as hyperlipidemia, osteoporosis, and viral hepatitis. MODERN NUTRITION IN HEALTH ANDDISEASE, 1447 (Shils et al., eds., 9th ed. 1999).
Nutritional intervention is critical to the management of chronic renal disease and end-stage renal disease. Dietary therapy should maintain or improve the nutritional status of the renal patient and minimize or prevent uremic and metabolic toxicities associated with renal failure. The challenge is to simplify a complex dietary regimen while providing an effective nutritional treatment. The nutritional compositions and related methods described herein include the numerous vitamins and minerals deficient in the restricted diet of the renal patient. Thus, the compositions and methods of the present invention offer to meet the nutritional needs of the renal patient in an uncomplicated approach.